There currently exist numerous arrangements for generating a plurality of isolated regulated output voltages from an input voltage. The first of them consists in using as many independent converters as regulated output voltages to be provided. Each converter generates a regulated output voltage from the unique input voltage and has, in order to generate this voltage, its own galvanic isolation component (transformer) and its own regulating loop. The cost of this arrangement is large, as are the proportions thereof, since it requires as many transformers as regulated output voltages. Moreover, the mutual synchronization of the various converters is tricky to achieve and requires the addition of further external components.
Another possible arrangement consists in wiring DC/DC converters that are preferably not isolated, up to the secondary side of a master converter that is isolated with transformer. The transformer of this master converter undertakes the galvanic isolation between the input voltage and the output voltages. The DC/DC converters are arranged in parallel on the output of the master converter. This arrangement becomes relatively complex when certain performances (low switch losses, synchronization of the DC/DC converters on the master converter) are sought.
Finally, another arrangement consists in using a single DC/DC converter comprising a single galvanic isolation transformer and in using, at the transformer level, as many secondary windings as regulated output voltages to be provided. For example, the transformer comprises a primary winding and two secondary windings, each secondary winding being used to produce a regulated output voltage. A switch is arranged in series with the primary winding. This switch is controlled by the output of a pulse width modulation circuit (PWM) receiving as input the voltage signal of one of the outputs of the converter. This device has the advantage of being simple to implement since it suffices to use as many windings at the secondary side of the transformer as regulated voltages desired, to rectify and filter each of them and to use one of them to slave the assembly. The problem with this arrangement is that only the output used for the slaving is perfectly regulated. The other outputs vary as a function of the loads present at their terminals and they have a tendency to increase at low load. The main drawback of this arrangement is therefore that it is rather ineffectual in terms of cross regulation between outputs.